Math Problem Statement

Find the fourth root of the square of the complex number z = 3 - 3i√3.

Solution

The image presents a complex number z=33i3z = 3 - 3i\sqrt{3} and asks to find z24\sqrt[4]{z^2}, the fourth root of the square of zz.

Let's break it down:

  1. Step 1: Calculate z2z^2
    We need to square the complex number z=33i3z = 3 - 3i\sqrt{3}.

    z2=(33i3)2z^2 = (3 - 3i\sqrt{3})^2

    Expanding this expression:

    z2=322(3)(3i3)+(3i3)2z^2 = 3^2 - 2(3)(3i\sqrt{3}) + (3i\sqrt{3})^2 z2=918i3+(9)(3)z^2 = 9 - 18i\sqrt{3} + (9)(-3) z2=918i327z^2 = 9 - 18i\sqrt{3} - 27 z2=1818i3z^2 = -18 - 18i\sqrt{3}

  2. Step 2: Find the fourth root of z2z^2
    We now need to find 1818i34\sqrt[4]{-18 - 18i\sqrt{3}}. To do this, it's easier to convert the complex number into polar form.

    The complex number 1818i3-18 - 18i\sqrt{3} can be written as r(cosθ+isinθ)r(\cos \theta + i \sin \theta), where:

    • r=(18)2+(183)2=324+972=1296=36r = \sqrt{(-18)^2 + (-18\sqrt{3})^2} = \sqrt{324 + 972} = \sqrt{1296} = 36,
    • The argument θ\theta can be calculated as θ=tan1(18318)=tan1(3)=2π3\theta = \tan^{-1}\left(\frac{-18\sqrt{3}}{-18}\right) = \tan^{-1}(\sqrt{3}) = \frac{2\pi}{3}.

    So, in polar form:

    z2=36(cos(2π3)+isin(2π3))z^2 = 36 \left( \cos\left(\frac{2\pi}{3}\right) + i \sin\left(\frac{2\pi}{3}\right) \right)

  3. Step 3: Apply the fourth root
    To find z24\sqrt[4]{z^2}, we take the fourth root of both the modulus and the argument:

    • The modulus becomes 364=6\sqrt[4]{36} = \sqrt{6},
    • The argument becomes 14×2π3=π6\frac{1}{4} \times \frac{2\pi}{3} = \frac{\pi}{6}.

    Therefore, z24\sqrt[4]{z^2} in polar form is:

    z24=6(cos(π6)+isin(π6))\sqrt[4]{z^2} = \sqrt{6} \left( \cos\left(\frac{\pi}{6}\right) + i \sin\left(\frac{\pi}{6}\right) \right)

    Simplifying:

    z24=6(32+i12)\sqrt[4]{z^2} = \sqrt{6} \left( \frac{\sqrt{3}}{2} + i \cdot \frac{1}{2} \right) z24=182+i62\sqrt[4]{z^2} = \frac{\sqrt{18}}{2} + i\frac{\sqrt{6}}{2}

    Hence, z24\sqrt[4]{z^2} is:

    182+i62\boxed{\frac{\sqrt{18}}{2} + i \frac{\sqrt{6}}{2}}

Let me know if you would like a more detailed explanation or have any questions!

Here are some related questions:

  1. How do you find the square of a complex number geometrically?
  2. How do you convert a complex number into polar form?
  3. What is the process of extracting the nn-th root of a complex number?
  4. What is the significance of Euler's formula in complex number operations?
  5. Can you generalize the process of finding the fourth root of any complex number?

Tip: When working with complex numbers, converting to polar form can simplify powers and roots considerably.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Polar Form
Roots of Complex Numbers

Formulas

z^2 = (3 - 3i√3)^2
Polar form: r(cos(θ) + i sin(θ))
Fourth root of complex number: √[4]{r} and θ/4

Theorems

De Moivre's Theorem
Euler's Formula

Suitable Grade Level

Undergraduate Mathematics